Sea Harvest Fish Market is just as close as Starbucks and the fast food (in the Crossroads Center on Rio Rd about a mile north of the park off of Highway 1; next stoplight to the North, I believe); has a patio, is casual and has healthy (though not necessarily dirt cheap) alternatives, and is open for lunch weekends.

However, I would picnic at Lobos. Much better view, and once you get there you won't want to leave!

You could pick up picnic supplies (weather permitting) at Safeway or Whole Foods. There are tables in the park. Also, the California Market at the Highlands Inn is great in all respects, food, view and atmosphere. It is a couple miles from the park.